Pulse oximeters have gained rapid acceptance in a wide variety of medical applications, including surgical wards, intensive care units, general wards and home care by providing early detection of decreases in the arterial oxygen supply, reducing the risk of accidental death and injury. FIG. 1 illustrates a pulse oximetry system 100 having a sensor 110 applied to a patient, a monitor 120, and a patient cable 130 connecting the sensor 110 and the monitor 120. The sensor 110 has emitters (not shown) and a detector (not shown) and is attached to a patient at a selected fleshy medium site, such as a fingertip 10 as shown or an ear lobe. The emitters are positioned to project light of at least two wavelengths through the blood vessels and capillaries of the fleshy medium. The detector is positioned so as to detect the emitted light after absorption by the fleshy medium, including hemoglobin and other constituents of pulsatile blood flowing within the fleshy medium, generating at least first and second intensity signals in response. A pulse oximetry sensor is described in U.S. Pat. No. 6,256,523 entitled Low Noise Optical Probes, and a pulse oximetry monitor is described in U.S. Pat. No. 6,745,060 entitled Signal Processing Apparatus, both assigned to Masimo Corporation, Irvine, Calif. and both incorporated by reference herein.
The monitor 120, which may be a standalone device or may be incorporated as a module or built-in portion of a multiparameter patient monitoring system, computes at least one physiological parameter responsive to magnitudes of the intensity signals. A monitor 120 typically provides a numerical readout of the patient's oxygen saturation 122, a numerical readout of pulse rate 124, and a display of the patient's plethysmograph 126, which provides a visual display of the patient's pulse contour and pulse rate.
In one embodiment, the pulse oximetry system 100 has a portable instrument 210 and a docking station 220, such as described in U.S. Pat. No. 6,584,336 entitled Universal/Upgrading Pulse Oximeter, assigned to Masimo Corporation, Irvine, Calif. and incorporated by reference herein. The portable 210 is a battery operated, fully functional, stand-alone pulse oximeter monitor, as described above, which can be installed into the docking station 220 to expand its functionality.
FIG. 2 illustrates data communications for the portable 210 and docking station 220. The portable 210 has bi-directional serial data communications with the docking station 220 using universal asynchronous receive, Rx0, and transmit, Tx0, (UART) signals, and the docking station 220 has bi-directional serial data communications with an external device 230 using Tx1 and Rx1 UART signals.